判断银行卡号是否有效

+ (BOOL) isValidCreditNumber:(NSString*)value {

02. BOOL result = NO;

03. NSInteger length = [value length];

04. if (length >= 13) {

05. result = [WTCreditCard isValidNumber:value];

06. if (result)

07. {

08. NSInteger twoDigitBeginValue = [[value substringWithRange:NSMakeRange(0, 2)] integerValue];

09. //VISA

10. if([WTCreditCard isStartWith:value Str:@"4"]) {

11. if (13 == length||16 == length) {

12. result = TRUE;

13. }else {

14. result = NO;

15. }

16. }

17. //MasterCard

18. else if(twoDigitBeginValue >= 51 && twoDigitBeginValue <= 55 && length == 16) {

19. result = TRUE;

20. }

21. //American Express

22. else if(([WTCreditCard isStartWith:value Str:@"34"]||[WTCreditCard isStartWith:value Str:@"37"]) && length == 15){

23. result = TRUE;

24. }

25. //Discover

26. else if([WTCreditCard isStartWith:value Str:@"6011"] && length == 16) {

27. result = TRUE;

28. }else {

29. result = FALSE;

30. }

31. }

32. if (result)

33. {

34. NSInteger digitValue;

35. NSInteger checkSum = 0;

36. NSInteger index = 0;

37. NSInteger leftIndex;

38. //even length, odd index

39. if (0 == length%2) {

40. index = 0;

41. leftIndex = 1;

42. }

43. //odd length, even index

44. else {

45. index = 1;

46. leftIndex = 0;

47. }

48. while (index < length) {

49. digitValue = [[value substringWithRange:NSMakeRange(index, 1)] integerValue];

50. digitValue = digitValue*2;

51. if (digitValue >= 10)

52. {

53. checkSum += digitValue/10 + digitValue%10;

54. }

55. else

56. {

57. checkSum += digitValue;

58. }

59. digitValue = [[value substringWithRange:NSMakeRange(leftIndex, 1)] integerValue];

60. checkSum += digitValue;

61. index += 2;

62. leftIndex += 2;

63. }

64. result = (0 == checkSum%10) ? TRUE:FALSE;

65. }

66. }else {

67. result = NO;

68. }

69. return result;

70. }